Lead anchor for a neuromodulation lead

ABSTRACT

A lead anchor for a neuromodulation lead has an anchor body that receives a portion of the lead. A mesh is arranged so as to at least partially surround the portion of the lead when the portion of the lead is received in the anchor body.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/593,230, filed on Oct. 4, 2019, which claims the benefit,under 35 U.S.C. § 119(e), of provisional patent application No.62/741,787, filed Oct. 5, 2018; the prior applications being herewithincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The instant invention generally relates to a lead anchor for aneuromodulation lead. In particular, the instant invention also relatesto an implantable lead anchor being configured to reversibly clamp aspinal cord stimulation lead.

Neuromodulation consists of the delivery of electrical, magnetic,mechanical, thermal, or optical stimuli to the central or peripheralnervous system of a patient. To this end, an implantable medical devicemay be implanted in the patient's body, wherein the implantable medicaldevice is configured for stimulating neural tissue, e.g., by means ofone or more electrodes being arranged inside one or more leads.

A common example of such an implant-based neuro therapy is the spinalcord stimulation (SCS), in which case the implantable medical devicecomprises an implantable pulse generator (IPG) and typically two leads.The leads extend along the spinal cord and have a plurality ofelectrodes (for example eight electrodes per lead) that couple to theneural tissue at different locations in the spinal cord

SCS is an emerging technique for providing long-term pain relief to apatient as an alternative to medication in cases where correctivesurgery is no longer an option. The effectiveness of SCS is dependentupon the positioning of two sets of electrodes at the end of conductiveleads within the spinal column. The location of the electrodes relativeto each other and the spinal cord is paramount to successful therapy.During normal patient activity, the leads will experience stresses thatcan cause the leads to migrate. Migration of a lead may result in anunwanted change or loss of therapy, requiring a corrective action.

The problem presented by lead migration is conventionally addressedthrough the application of an anchoring device that is designed tosecure the lead to the fascia at the point where the lead enters intothe spinal column. For example, to ensure that the leads do not moveonce they have been placed, such an anchoring device may be placed alonga portion of the lead.

A traditional “passive” lead anchoring system is most often comprised ofa silicone body which has a hollow cylindrical portion (which may alsobe referred to as lumen) where the lead is passed through. There areoften eyelets provided on the anchor so that it can be fixed in placewith sutures. The traditional anchors are typically employed to keep theleads in a relatively secure position. However, they do not provideresistance to axial forces, which in the case of SCS lead is the maincause of lead migration. It is for this reason desirable that anchorsare designed to have an activated locking mechanism specifically toprevent axial motion of the leads.

Further, the initial positioning of each lead is subject to changeduring the initial operation and during the lifetime of the therapy. Itis therefore desirable that the anchoring system has the ability tounlock, reposition and relock at the physicians' discretion.

Active lead anchor solutions that are currently available utilizesemi-permanent locking mechanisms. Some are irreversible, using, e.g.,adhesive to fix the anchor to a lead for ensuring that the lead positiondoes not change once the anchor is placed. For example, the U.S. Pat.No. 9,216,563 B2 proposes an adhesive-based solution.

Other solutions have snapping mechanisms which ‘click’ into placethrough twisting or pinching a portion of the lead anchor relative toanother portion of the lead anchor. These solutions are hand actuatedand do not require unique tools to manipulate.

A few solutions exist where a set screw is articulated and the lead iscompressed under the screw tip by either the screw itself or by aprotective polymer sleeve or pressure plate.

Due to the relative complexity and unique designs associated with thelead system, most of the existing anchor solutions are unique to thelead that they are designed to secure.

The existing lead anchor concepts mentioned above have the followingdrawbacks:

Anchors which require adhesion are challenging in the case where thelead would require adjustment for improved therapy. In that case, theanchor would have to be cut from the lead and a new anchor would thenhave to be placed along the lead at a new position.

Further, some known solutions may require a special handling tool thatis used specifically with the anchor and has no other function to aphysician. For example, the U.S. Pat. No. 9,433,755 B2 describes adedicated anchor deployment assembly. Such tools may require additionaltraining to ensure proper usage. In the case of removal and replacementthe risk of lead migration may be significant.

The solutions that use ‘clicking’ or hand actuated mechanisms run therisk of patient actuation during the lifetime of the device. This couldoccur without the patient being aware and would likely result in leadmigration and ultimately a corrective operation. Additionally, the handactuation usually requires that the lead anchor be free from tissue andpresents a risk of causing the electrodes to move under the actuationforce of the locking mechanism.

There are embodiments that utilize set screw to compress the lead bodyor a protective sleeve around the lead. For example, the U.S. Pat. No.9,352,147 B2 discloses a lead anchor comprising a sleeve that isdeformable by a fastener so as to obstruct a lead lumen and keep a leadbody that is arranged therein in place.

Generally, the technique of manipulating the lead under the action of aset screw must be carefully considered. If unrestrained, contact betweenthe set screw and the lead may cause damage to the lead resulting in theloss of its ability to provide therapy. For example, the lead system maybe irreversibly (i.e., permanently) changed under the influence of theset screw. As a result, once the anchor is actuated, removal of theanchor may require replacement of the lead.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved leadanchor, which overcomes the drawbacks of known solutions. In particular,due to the relative complexity and fragility of the lead, it isdesirable for an anchor to be able to secure the lead in place withoutcausing undue stress to the lead body while performing its desiredfunction. For example, it is desirable to eliminate the risk ofirreversible effects on the lead system or unintentional unlocking ofthe lead anchor.

With the above and other objects in view there is provided, inaccordance with the invention, a lead anchor for a neuromodulation lead,which comprises an anchor body that is configured to receive a portionof the lead, and a mesh that is arranged so as to at least partiallysurround the portion of the lead when the portion of the lead isreceived in the anchor body. The mesh may comprise (or, consist of) ametal.

For example, the mesh may be arranged in contact with said portion ofthe lead. Hence, a material interface in the form of said mesh may bearranged within the lead anchor. The material interface may providedistributed contacts along the lead body. Thus, friction between thelead and the anchor may be increased, thereby providing grip to resistaxial forces and preventing lead migration. In other words, the mesh mayenable a distributed loading of the lead body, thus preventing acutemechanical damage. Due to the fact that the interface material isprovided in the form of a mesh, adequate flexibility and grip on thelead may be advantageously combined.

For example, the mesh may be compressible. Thus, the requiredflexibility to conform to complex internal lead geometries may beprovided.

In an embodiment, the mesh is reversibly (e.g., elastically) deformable.For example, the mesh may return to its original form when a lockingmechanism of the lead anchor is released.

In an embodiment, the mesh has a shape memory function and/or comprisesan elastic material. For example, the mesh may comprise or consist of amaterial such as, e.g., nitinol. Nitinol is highly flexible understress, but when released from a loading condition will return to itsoriginal shape. The inclusion of a compressible mesh made from memorymetal may provide a fully reversible lead anchor solution. Thisfunctionality provides direct advantages including reversibility andflexibility over the expected lifetime of the implantable medicaldevice.

According to an embodiment, the lead anchor comprises a clampingelement, which may in turn comprise the mesh. Thus, the clamping elementmay be configured to reversibly clamp a portion of the lead by means ofa reversible deformation of the mesh. For example, the clamping of thelead (via the mesh) may hinder an axial displacement of the leadrelative to the anchor body of the lead anchor. With such a solution,the process of securing the lead may be reversible over the lifetime ofthe anchor so that if the therapeutic system needs change, the leadposition can be adjusted without removal of the lead or anchoring systementirely.

In an embodiment, the clamping element comprises an actuator beingconfigured to reversibly activate the clamping function of the clampingelement. For example, the actuator may be configured to induce areversible deformation of the mesh. The ability to reverse the lockingmechanism of the lead anchor provides flexibility to the implantationprocedure and facilitates lead repositioning. To ensure that the lead isnot damaged by the activation mechanism (i.e., the actuator), saidmaterial interface in the form of the mesh may be included within theanchor, which will compress and conform to the outer surface of the leadbody without constricting the conductors within the lead body. Thereversibility of the anchoring system may remove any risk of damagingthe lead during removal of the anchor or migration of the lead duringactivation or deactivation which could occur in the semi-permanent andhand actuated solutions.

In a variant of the embodiment mentioned above, the actuator is orcomprises a set screw, which may impinge, e.g., on the mesh. Forexample, the set screw may be activated by means of a torque wrench. Setscrews and torque wrenches are common tools used in connecting leads toimplantable pulse generators and are hence generally available in thefield. A set screw actuator may thus reduce the need for an additionaltool and special training which is generally required in the case ofsolutions which utilize custom staples, or other mechanisms.

For example, the set screw activation may ‘lock’ the lead into place bycreating contact with the lead. According to the present invention, forexample, the compressible mesh may be included between the set screw andthe lead body so as to avoid damage to the lead. The set screw may thusprovide a secure locking mechanism that cannot be unlocked withoutdirect articulation of the screw using a torque wrench.

For example, in a further variant embodiment, the lead anchor may bedesigned specifically to accommodate a custom magnetic resonance imaging(MRI) compatible lead. Such an MRI lead may have sections that arefundamentally different in contour and rigidity from usual SCS leads.The discontinuous nature of the MRI lead provides an additionalcomplexity to the solution requirements. For example, the engagementwith the anchor during activation must be flexible enough to constrictrigid and soft portions of a SCS lead without losing its functionalityin either case.

According to an embodiment, the clamping element is configured as aC-clamp. Accordingly, for example, the clamping element may comprise aC-clamp body, wherein the mesh may form at least a part of a C-shapedlead support portion of the C-clamp body. For example, the mesh may havea C-shaped cross-section.

In an embodiment in accordance with the above-mentioned variant, anactuated set screw as described above may impinge on a portion of theC-clamp, such as directly on the mesh.

According to another variant embodiment, the mesh forms a sleeve beingconfigured to receive a portion of the lead. For example, in accordancewith this variant, the lead anchor may comprise a set screw collar(forming, e.g., a part of a clamping element as described above),wherein the sleeve may be at least partially arranged inside the setscrew collar. In other words, the sleeve-shaped mesh may be arranged asan inlay inside the set screw collar.

The anchor body may define a lumen for receiving a portion of theneuromodulation lead. For example, the anchor body may comprise (e.g.,consist of) silicone. Further, it may be provided that the anchor bodyhas at least one fastener portion, e.g., in the form of one or moreeyelets. The fastener portion(s) may be configured for fastening theanchor body to the tissue of a patient. For example, the fastenerportions may be attached to the fascia of the patient, e.g., by means ofa suture.

Summarizing, in accordance with the present invention, a fullyreversible, set screw activated lead anchor for spinal cord stimulationsystem may be provided. By using a mesh, which may be formed, e.g., of ashape memory metal, the present invention enables a lead anchoringmechanism that provides adequate retention forces on a (potentiallydiscontinuous) lead body while reducing the complexity of an operatingprocedure.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a lead anchor for a neuromodulation lead, it is nevertheless notintended to be limited to the details shown, since various modificationsand structural changes may be made therein without departing from thespirit of the invention and within the scope and range of equivalents ofthe claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1A is a schematic perspective view of an exemplary lead anchoraccording to one or more embodiments of the invention;

FIG. 1B is a schematic longitudinal cross-section through a clampingelement of the lead anchor of FIG. 1A;

FIG. 2A is a schematic side view of an exemplary lead anchor inaccordance with one or more further embodiments of the invention; and

FIG. 2B illustrates a perspective view of the lead anchor of FIG. 2A.

Like reference numerals designate like structural elements throughoutthe figures of the drawing. Further, it will be noted that theillustrated embodiments are not limiting for the invention, but theymerely represent illustrative examples.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1A thereof, there is shown a schematic andexemplary perspective view of a lead anchor 1 for a neuromodulation lead2 in accordance with one or more embodiments. More precisely, anarrangement of a lead 2 and a lead anchor 1 is shown in a state whereinthe lead 2 is secured to the lead anchor 1.

The lead anchor 1 has an elongate anchor body 10, which may, forexample, comprise or consist of silicone. For the purpose ofillustration, the anchor body is depicted transparent in FIG. 1A. Thatis, while the contours of the anchor body 10 are shown, structures thatare arranged inside the anchor body 10 are also illustrated.

The anchor body 10 defines a lumen 102 that is configured for receivinga portion of the lead 2. Further, the anchor body 10 has fastenerportions 101 in the form of eyelets for fastening the anchor body 10 toa patient's tissue (e.g., fascia) by means of a suture. For example, thelead anchor device may thus be configured to secure the lead 2 to thefascia at the point where the lead enters into the spinal column.

The illustrated lead anchor 1 is equipped with an active anchor lockingmechanism which allows for locking the lead 2 inside the anchor body 10.This is to say that the locking mechanism of the lead anchor 1 may beactivated to prevent axial motion of the leads relative to the anchorbody 10. To this end, a clamping element 12 of the lead anchor 1 isprovided.

In the exemplary embodiment shown in FIG. 1A, the clamping element 12comprises a set screw collar 121 and an associated set screw 124. Theset screw collar 121 defines a lumen 1210, which is axially aligned withthe lumen 102 of the anchor body 10, such that the lead 2 may extendthrough the lumen 102 of the anchor body 10 as well as through the lumen1210 of the set screw collar 121, as illustrated.

The set screw 124 may be (reversibly) activated, e.g., by means of atorque wrench, to clamp the portion of the lead 2 extending inside thelumen 1210 of the set screw collar 121. In other words, the set screw124 serves as an actuator that is configured to reversibly activate theclamping function of the clamping element 12. The clamping mechanism ofthe clamping element 12 will be explained in some more detail in thefollowing with reference to FIG. 1B.

FIG. 1B shows a longitudinal (i.e., axial) cross-section through theclamping element 12 of the lead anchor 1 of FIG. 1A. The cross-sectionshows the set crew collar 1210 including its lumen 1210, as well as theset screw 124.

Further, the cross-sectional view in FIG. 1B reveals that the clampingelement 12 comprises a mesh 123 in the form of a sleeve. The sleeve 123is arranged as an inlay inside the lumen 1210 of the set screw collar121, such that a portion of the lead 2 may extend through the sleeve123. In other words, the mesh 123 may (at least partially) surround theportion of the lead 2 when the latter extends inside the anchor body 10.Further, in that case, the mesh 123 may be arranged in direct contactwith the portion of the lead 2.

By way of example, the mesh 123 may comprise or consist of a metal,e.g., a shape memory metal such as nitinol.

Further, the mesh 123 may be compressible, such that it compresses underthe force of the set screw 124. In this way, the force exerted on thecompressible mesh 123 may be distributed along the lead body 2 so as toeliminate the possibility of damaging the lead body 2 or conductors thatmay be arranged therein. Hence, the clamping element 12 may beconfigured to reversibly clamp a portion of the lead body 2 by means ofa reversible deformation of the mesh 123, which is induced by theactivation of the set screw 124. Thereby, the mechanical force exertedby the set screw 124 may be distributed over the whole mesh area of themesh 123.

The geometric mesh pattern is advantageous because it creates stressrelief points along the surface of the lead body 2. This may allowportions of an outer tubing (consisting, e.g., of polyethylene) of thelead body 2 to fill in the gaps in the mesh 123. This may further reducestress on the lead conductors and increase the anchor's 1 grip on thelead body 2.

The use of a metal mesh 123 having a shape memory function has theadvantage that the mesh 123 can withstand high levels of stress and willreturn to its original uncompressed state once the set screw 124 is nolonger pressing on the mesh 123. This provides a highly reversible leadanchor solution, allowing placement and removal of the lead anchor 1during the entire operational life time of the lead anchor 1.

FIG. 2A is a schematic and exemplary side view of a lead anchor 1 inaccordance with one or more further embodiments. FIG. 2B schematicallyand exemplarily illustrates a perspective view of the lead anchor 1 ofFIG. 2A. In the following, reference will be made to both FIG. 2A andFIG. 2B.

In the exemplary embodiments of FIGS. 2A and 2B, the anchor body 10 ifthe lead anchor 1 is similar to the anchor body 10 described above withreference to FIGS. 1A and 1B.

The embodiment of FIGS. 2A and 2B differs from the one of FIGS. 1A and1B in that the clamping element 12 of the activated lead anchor 1 isconfigured as a C-clamp. An actuator 124 in the form of a set screw isconfigured to (reversibly) compress two flanges of a C-clamp body 122.Thus, a portion of a lead body 2 extending through a C-shaped leadsupport of the C-clamp body 122 may be clamped (i.e., ‘locked’).

In the exemplary embodiment of FIGS. 2A-B, the C-shaped lead supportsection of the C-clamp body 122 is provided in the form of a mesh 123.Accordingly, in this embodiment, the mesh 123 may have a C-shapedcross-section.

For more details and properties of the mesh 123, e.g., with regard topossible materials, it is referred to the above description inconnection with FIGS. 1A-B. The mesh 123 of the present embodiment mayhave analogous advantages as the ones described above. For example, asexplained earlier with reference to FIGS. 1A-B, when the C-shaped leadsupport (i.e., the mesh 123) compresses under the action of the setscrew 124, the mesh 123 may advantageously provide a distributedcompression along the lead body 2 without damaging the lead conductors.

In principle, however, the C-shaped lead support may consist of anysuitable material, i.e., not necessarily of a mesh 123. For example, theC-shaped lead support could be made of a memory metal or anotherflexible material providing sufficient reversibility, wherein theC-shaped lead support may not necessarily have a mesh-shape.

It is also conceivable that a mesh 123 as described above be providedadditionally as an inlay inside a C-shaped lead support. For example, inthis case, the inlay mesh may be provided as a sleeve 123, as describedabove with reference to FIG. 1B. Alternatively, such an inlay mesh mayhave a C-shaped cross-section, for example.

It will be apparent to those skilled in the art that numerousmodifications and variations of the described examples and embodimentsare possible in light of the above teaching. The disclosed examples andembodiments are presented for purposes of illustration only. Otheralternate embodiments may include some or all of the features disclosedherein. Therefore, it is the intent to cover all such modifications andalternate embodiments as may come within the true scope of thisinvention.

The following is a summary list of reference numerals and thecorresponding structure used in the above description of the invention:

-   -   1 Lead anchor    -   10 Anchor body    -   101 Fastener portion    -   102 Lumen of the anchor body    -   12 Clamping element    -   121 Set screw collar    -   1210 Lumen of the set screw collar    -   122 C-clamp body    -   123 Mesh    -   124 Actuator    -   2 Lead body

1. A lead anchor for a neuromodulation lead, the lead anchor comprising:an anchor body configured to receive a portion of the neuro-modulationlead; and a compressible mesh disposed to at least partially surroundthe portion of the neuromodulation lead when the portion of theneuromodulation lead is received in the anchor body.
 2. The lead anchoraccording to claim 1, wherein the mesh comprises a metal.
 3. The leadanchor according to claim 1, wherein the mesh has a shape memoryfunction.
 4. The lead anchor according to claim 1, wherein the meshcomprises nitinol.
 5. The lead anchor according to claim 1, furthercomprising a clamping element containing said compressible mesh, saidclamping element being configured for reversibly clamping a portion ofthe neuromodulation lead by way of a reversible deformation of saidcompressible mesh.
 6. The lead anchor according to claim 5, wherein saidclamping element comprises an actuator configured to reversibly activatea clamping function of said clamping element.
 7. The lead anchoraccording to claim 6, wherein said actuator is or comprises a set screw.8. The lead anchor according to claim 5, wherein said clamping elementis a C-clamp.
 9. The lead anchor according to claim 8, wherein saidclamping element comprises a C-clamp body, and said compressible meshforms at least a part of a C-shaped lead support portion of said C-clampbody.
 10. The lead anchor according to claim 1, wherein saidcompressible mesh has a C-shaped cross-section.
 11. The lead anchoraccording to claim 1, wherein said compressible mesh forms a sleeve thatis configured to receive the portion of the neuromodulation lead. 12.The lead anchor according to claim 11, further comprising a set screwcollar, wherein said sleeve is at least partially arranged inside saidset screw collar.
 13. The lead anchor according to claim 1, wherein saidanchor body defines a lumen for receiving the portion of theneuromodulation lead.
 14. The lead anchor according to claim 1, whereinsaid anchor body has at least one fastener portion configured to fastensaid anchor body to tissue of a patient.